Low profile turntable assembly

ABSTRACT

A large rectangular rotary table includes a fabricated tubular metal frame having top plates for supporting fixtures and large motor vehicle parts. A center portion of the table frame is supported by an annular turret bearing mounted on a base plate spaced above a floor plate by adjustable leveling screws. A drive unit is also supported by the base plate within the bearing and the center portion of the table frame and includes a planocentric gear reducer driven by an electric servo motor projecting above the table. A laterally projecting torque arm is mounted on the output of the gear reducer and is connected to the table frame by a sliding drive pin assembly which prevents radial loads on the gear reducer when the table is indexed. A fluid actuated table locating pin alternately engages a locating seat on each end of the table after the table is indexed.

BACKGROUND OF THE INVENTION

The present invention relates to a large, heavy-duty turntable assemblyof the type used for transferring or indexing heavy workpieces or partssuch as motor vehicle parts. Such turntable assemblies are generallydisclosed, for example, in U.S. Pat. No. 4,285,233, No. 4,795,021 andNo. 6,435,397. In this type of turntable assembly which may be used totransfer motor vehicle frames or body parts to robotic welders, it ishighly desirable for the assembly to have a low profile above the floorwithout requiring a pit within the floor to receive an indexing drivemechanism so that the assembly may be located anywhere in amanufacturing plant. A low profile turntable is also desirable in orderto avoid using man stands or platforms for the operators to work and/orto avoid the need to elevate the heavy parts when loading the parts ontoan elevated turntable and the need to lower the parts from theturntable.

A low profile turntable also provides for operator ergonomics andenables the turntable to be conveniently used and serviced. This isespecially desirable when the parts being loaded, transferred andunloaded have substantial weight such as several thousand pounds, andthe tools or fixtures which are mounted on the turntable for supportingthe parts also have substantial weight, for example, five thousand tosix thousand pounds. It is further desirable for a loaded turntable torotate or index or oscillate quickly and precisely so that there isminimal down time of the equipment adjacent the turntable, such asrobotic welders, which perform operations on the parts after they areindexed or transferred.

SUMMARY OF THE INVENTION

The present invention is directed to an improved turntable assemblywhich provides all of the desirable features mentioned above and whichespecially provides for transferring or indexing tooling or fixtures andparts having combined weights of many thousand pounds and which also hasa very low profile to facilitate loading heavy parts onto the turntableand unloading parts from the turntable. The turntable assembly of theinvention is also capable of quickly indexing or oscillating in a timeperiod of only a few seconds and further provides for preciseregistration of the table after indexing.

In accordance with one embodiment of the invention, a turntable assemblyincludes a generally horizontal base plate for mounting on a floor, anda fabricated tubular metal frame having a plurality of spaced supportsfor mounting tooling or fixtures. The table frame is supported by anannular turret bearing mounted on the base plate, and a drive unit hasan output supported by the base plate within the bearing and a centerportion of the table frame. The drive unit rotates the table frame andincludes a speed reducer and an electric servo motor which projectsupwardly from the center portion of the table. The speed reducer isconnected to a laterally projecting torque member or arm, and a verticaldrive pin connects the torque arm to the table frame.

Other features and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a low profile turntable assemblyconstructed in accordance with the invention;

FIG. 2 is a section of the assembly taken generally on the line 2-2 ofFIG. 1;

FIG. 3 is a fragmentary section taken generally on the line 3-3 of FIG.2;

FIG. 4 is a fragmentary section taken generally on the line 4-4 of FIG.1; and

FIG. 5 is a fragmentary section of a floor plate and the adjustable baseor support plate shown in FIGS. 2-4.

DESCRIPTION OF ONE PREFERRED EMBODIMENT

FIG. 1 illustrates a low profile turntable assembly 10 which includes anelongated rectangular fabricated steel table frame 12 having a pair oflongitudinally extending members or rails 14 formed of steel tubing witha rectangular cross-section, as shown in FIG. 2. The parallel spacedrails 14 are rigidly connected by cross frame members 16 which are alsoformed of rectangular steel tubing and which are welded to the siderails 14. The cross frame members 16 are also rigidly connected bylongitudinally extending frame members 18 which are formed fromrectangular steel tubing and welded to the cross members 16. A pair oflongitudinally extending steel top plates 22 are welded to the top ofside rails 14, and a pair of longitudinally spaced fixture supportmembers or plates 24 are welded to the top surfaces of the frame members16 and 18 on each end portion of the table frame 12.

The table frame 12 is supported for rotation on a vertical center axis26 (FIG. 2) by the annular outer race 28 of a large diameter turretbearing 30, for example, of the type manufactured and sold under thetrademarks Kaydon and Rotek. The outer bearing race 28 is secured byscrews 29 to an annular support plate 32 which is secured or welded to aset of opposing side plates 34 projecting under the top plates 22 andwelded to the top plates. The turret bearing 30 has an annular innerrace 38 which is secured by screws 39 to an annular base plate 40. Thebase plate 40 is supported by a floor plate 42 through a plurality ofadjustable jack screws 44 (FIG. 5) which are threaded into the baseplate 40 and are secured by lock nuts 46. After the floor plate 42 islocated in a plant on the plant floor, the table 12 is leveled with therotational axis 26 precisely vertical by adjusting the jack screws 44 tolevel the base plate 40. If it is desired to secure the table frame 12in the level position, the base plate 40 is welded to weld blocks orangle brackets 48 (FIG. 5) which are, in turn, welded to the floor plate42.

The table frame 12 is rotated or indexed on the axis 26 through 180° bya drive unit or assembly 55 which rotates with the table frame and has adownwardly projecting non-rotating output shaft secured to a circularplate 58 mounted within a recess in a circular bottom plate 60 securedby screws to the base plate 40. The drive unit 55 includes a speedreducer 64 of the type manufactured by SEW-Eurodrive, Inc. in Troy, Ohioand coupled to a planocentric robotic speed reducer 65 of the typemanufactured by Nabtesco Motion Control, Inc. in Novi, Mich. The speedreducer 64 is driven by the output shaft of an electrical closed loopservo motor 68, such as a robotic servo motor produced by Fanuc as a 7thaxis alpha 30/3000i. The motor power cable and encoder cable (not shown)project upwardly from the motor 68 and are adapted to twist when thetable frame 12 and drive unit 55 oscillate through an angle of 180°.

The speed reducer 65 has a stepped cylindrical base 72 which rotatesrelative to the plates 58 and 60 and supports a torque member or arm 74which is secured to the speed reducer base 72 by circumferentiallyspaced screws 76. The torque plate 74 carries a hardened and grounddrive pin 78 (FIG. 3) which has an outwardly projecting flange 81secured to the torque arm 74 by screws. The pin 78 has a downwardlyprojecting portion 82 which supports for rotation a square bronze driveshoe 84. The drive shoe 84 is captured between a pair of flame hardenedsteel drive plates 86 having ground parallel spaced faces engaging thedrive shoe. The drive plates 86 are secured to the table plate 32 by aset of screws, and the drive shoe 84 is able to slide radially betweenthe drive plates 86 to prevent radial loading on the torque arm 74 andthe base 72 of the speed reducer 65 when the table 12 is indexed orrotated in response to actuation of the servo motor 68.

After the table frame 12 indexes 180°, the table frame is preciselylocated or registered by a locating or registry unit 90 (FIG. 4) whichincludes a horizontal cylindrical locating pin 92 having a tapered orfrusto-conical outer end portion 94. The pin is supported for axialmovement within a bearing sleeve 95 having an end flange 96 secured to asupport member or housing 98. The housing 98 has a bottom flange 101which is connected to the floor plate 42 by a set of adjustable jackscrews 44 for precisely positioning the axis of the locating pin 92 at apredetermined elevation relative to the table frame 12. Afteradjustment, the base plate 101 may be rigidly secured to the floor plate42 by welding a pair of angle blocks or brackets 48 to the base plate101 and the floor plate 42. The locating pin 92 has an inner end portionsecured by a screw 104 to a reciprocating piston 106 of a fluid or aircylinder 108 secured to the housing 98 by an annular mounting plate 109.As shown in FIGS. 1 & 4, a locating or registry block 114 is secured toeach end of the table frame 12 by support blocks 116 and 117, and eachblock 114 is formed with a V-shaped wedge locating seat 119. After thetable frame 12 is indexed 180°, the air cylinder 108 is actuated toextend the pin 92 until the end portion 94 wedges into the seat 119,thereby precisely locating the table frame 12 and the tooling and partscarried by the table frame.

From the drawings and the above description, it is apparent that aturntable assembly 10 constructed in accordance with the inventionprovides desirable features and advantages. For example, the turntableassembly is especially usable for transferring heavy motor vehicle partsor frames from a loading station to a welding and unloading station andfor transferring the parts 180° in a short period of time such as sixseconds. The table frame 12 is also constructed to support substantialloads such as tooling or fixtures mounted on the pads or plates 24 andhaving a weight, for example, of 8,000 pounds. The turntable assembly 10also eliminates the requirement for a pit to accommodate the drivemechanism, with the top of the table frame 12 spaced only inches abovethe floor, for example 12 inches. This low profile of the table frame 12greatly facilitates loading tooling or fixtures and parts onto the tableframe and unloading the parts from the tooling.

As another feature, the planocentric speed reducer 65 eliminatesbacklash and provides smooth and accurate positioning of the tableframe. Also all gear reduction is sealed within the housing of thereducer so that no gears are exposed and no lube system is required. Inaddition, all of the components of the drive unit 55 are removable fromthe top side of the table for convenient servicing. The drive of thetable frame 12 from the torque arm 74 with the pin 78 and radial slidingshoe 84 also eliminates any side loading on the speed reducer 65 as thetable frame is being rotated. The wedge locating or registering pin 92also cooperates with the locating seat 119 to assure precision locationof the table frame 12 after it has been indexed. The easily accessiblejack screws 44 further provide for conveniently leveling the table 12after which the base plate may be welded to the floor plate with theweld blocks or angle brackets 48.

While the form of turntable assembly herein described constitutes apreferred embodiment of the invention, it is to be understood that theinvention is not limited to this precise form of assembly, and thatchanges may be made therein without departing from the scope and spiritof the invention as defined in the appended claims.

1. A low profile turntable assembly adapted for transferring large partshaving substantial weight between work stations, said assemblycomprising a generally horizontal base plate adapted to be mounted on afloor, a fabricated metal table frame having a plurality of spacedsupport areas adapted to receive fixtures for supporting the parts, anannular turret bearing supported by said base plate and supporting saidtable frame for rotation on a vertical axis, a drive unit within saidbearing and a center portion of said table frame and supported by saidbase plate, said drive unit including a speed reducer driven by a motorand projecting upwardly above said table frame, said speed reducerhaving a rotary output connected to a torque member, and a drive memberspaced from said axis and connecting said torque member to said tableframe to produce rotation of said table frame in response to actuationof said motor.
 2. A turntable assembly as defined in claim 1 whereinsaid drive member comprises a drive pin having a vertical axis, and acoupling connecting said drive pin to said table frame and providing forslight radial movement of said table frame relative to said speedreducer when said table frame is rotated.
 3. A turntable assembly asdefined in claim 2 and including a drive shoe mounted on said drive pin,and set of spaced drive plates connected to said table frame andreceiving said drive shoe therebetween for radial movement.
 4. Aturntable assembly as defined in claim 1 wherein said speed reducercomprises a planocentric robotic gear reducer, and said electric motorcomprises an electric servo motor controllable by a robotic programmer.5. A turntable assembly as defined in claim 1 wherein said table frameis generally rectangular and has opposite end portions with said supportareas, and said table frame has longitudinally extending tubular steelframe members.
 6. A turntable assembly as defined in claim 1 whereinsaid center portion of said table frame surrounds said annular turretbearing and said speed reducer.
 7. A turntable assembly as defined inclaim 1 and including a floor support plate spaced below said baseplate, and a plurality of adjustable jack screws mounted on said baseplate and engaging said floor plate to provide for precisely levelingsaid table frame.
 8. A turntable assembly as defined in claim 7 andincluding a plurality of weld blocks adapted to be welded to said baseplate and said floor plate after said table frame is leveled.
 9. Aturntable assembly as defined in claim 1 and including a table locatingmember supported by a floor plate adjacent a locating seat on an outeredge portion of said table frame, and a power operated unit connected tomove said locating member between a retracted position spaced from saidtable frame and an extended position engaging said locating seat on saidtable frame for precisely locating said table frame.
 10. A turntableassembly as defined in claim 9 wherein said table locating membercomprises a locating pin having a generally horizontal axis and atapered end surface, a housing supporting said pin for axial movement, afluid cylinder connected to move said pin axially, and said locatingseat comprises a V-shaped surface positioned on said table frame toreceive said tapered end surface of said pin.
 11. A low profileturntable assembly adapted for transferring large parts havingsubstantial weight between work stations, said assembly comprising agenerally horizontal base plate adapted to be mounted on a floor, afabricated metal table frame having a plurality of spaced support areasadapted to receive fixtures for supporting the parts, an annular turretbearing supported by said base plate and supporting said table frame forrotation on a vertical axis, a drive unit within said bearing and acenter portion of said table frame and supported by said base plate,said drive unit including a planocentric speed reducer driven by anelectric servo motor and projecting upwardly above said table frame,said speed reducer having a rotary output connected to a torque member,a drive coupling spaced from said axis and connecting said torque memberto said table frame to produce rotation of said table frame in responseto actuation of said motor, and said drive coupling providing for slightradial movement of said table frame relative to said torque member whensaid table frame is rotated.
 12. A turntable assembly as defined inclaim 11 wherein said drive coupling includes a drive pin, a drive shoemounted on said drive pin, and set of spaced drive plates receiving saiddrive shoe therebetween for radial movement.
 13. A turntable assembly asdefined in claim 11 wherein said table frame is generally rectangularand has opposite end portions having plates forming said support areas,and said table frame has longitudinally extending tubular steel framemembers rigidly connected by steel cross frame members.
 14. A turntableassembly as defined in claim 11 wherein said center portion of saidtable frame surrounds said annular turret bearing and said speedreducer.
 15. A turntable assembly as defined in claim 11 and including afloor support plate spaced below said base plate, and a plurality ofadjustable jack screws mounted on said base plate and engaging saidfloor plate to provide for precisely leveling said table frame.
 16. Aturntable assembly as defined in claim 15 and including a plurality ofweld blocks adapted to be welded to said base plate and said floor plateafter said table frame is leveled
 17. A turntable assembly as defined inclaim 11 and including a table locating member supported adjacent alocating seat on an outer edge portion of said table frame, and a poweroperated unit connected to move said locating member between a retractedposition spaced from said table frame and an extended position engagingsaid locating seat on said table frame for precisely locating said tableframe.
 18. A turntable assembly as defined in claim 17 wherein saidtable locating member comprises a locating pin having a generallyhorizontal axis and a tapered end surface, a housing supporting said pinfor axial movement, a fluid cylinder connected to move said pin axially,and said locating seat is formed by a V-shaped surface positioned onsaid table frame to receive said tapered end surface of said pin.
 19. Alow profile turntable assembly adapted for transferring large partshaving substantial weight between work stations, said assemblycomprising a generally horizontal base plate adapted to be mounted on afloor, a fabricated metal rectangular table frame having opposite endportions with spaced support areas adapted to receive fixtures forsupporting the parts, an annular anti-friction turret bearing supportedby said base plate and supporting said table frame for rotation on avertical axis through 180 degrees, a drive unit within said bearing anda center portion of said table frame and supported by said base plate,said drive unit including a speed reducer driven by a servo motor andprojecting upwardly above said table frame, said speed reducer having arotary output connected to a torque member, and a drive member spacedlaterally from said axis and connecting said torque member to said tableframe to produce rotation of said table frame in response to actuationof said motor.
 20. A turntable assembly as defined in claim 19 whereinsaid drive member comprises a drive pin having a vertical axis, and acoupling connecting said drive pin to said table frame and providing forslight radial movement of said table frame relative to said speedreducer when said table frame is rotated.
 21. A turntable assembly asdefined in claim 19 and including a floor support plate spaced belowsaid base plate, and a plurality of adjustable jack screws mounted onsaid base plate and engaging said floor plate to provide for preciselyleveling said table frame.